A photodetector is an optoelectronic device that senses light and converts the sensed light into an electrical signal. Many different types of photodetectors are available in the market. Photodetectors are well-suited for use as optical receivers for receiving optical signals and converting them into electrical signals. For this reason, photodetectors are often used in optical communications networks for receiving optical data signals that have been transmitted over an optical fiber and for converting the optical data signals into electrical data signals.
Photodetectors are sometimes used as optical isolators to electrically isolate different parts of a system from one another while allowing these parts of the system to be in communication with one another via an optical coupling. An optical isolator is a device that allows signals to be optically transferred between circuits or systems while keeping those circuits or systems electrically isolated from each other. Optical isolators are used in a wide variety of communications systems, control systems, and monitoring systems. In a typical optical isolator, an optical transmitter of the optical isolator is used to convert an electrical signal into an optical signal, which is then optically transmitted over air or over an optical waveguide to a photodetector. The photodetector converts the optical signal back to an electrical signal. The optical transmitter is typically a laser diode or light emitting diode (LED). The photodetector is typically a photodiode, such as a p-intrinsic-n (P-I-N) diode or a P-N diode.
Optical isolators and other types of optical systems are sometimes used in industrial applications, such as automated manufacturing systems and transportation systems, for example. In these types of industrial applications, very high electrical currents are commonly used. For example, in some drive applications, very high electrical currents are switched on and off at high frequency to drive large motors. The switching of these high electrical currents can produce EMI that can detrimentally affect the performance of other electrical circuits or components of the systems.
Optical systems, by nature, are not highly susceptible to EMI. For that reason, they are well suited for use in such industrial systems, although they have not been widely used in industrial systems heretofore. Optical systems typically include electronic or optoelectronic components that can potentially be detrimentally affected by EMI. In order to protect these components from the potentially detrimental affects of EMI, EMI events need to be sensed or monitored to determine when protective actions need to be taken or to determine changes that need to be made to the system to prevent future EMI events from detrimentally affecting system performance. Accordingly, a need exists for an EMI sensor and method for use in optical systems that are used in industrial applications.